<template>
  <div class="upload-excel">
    <input ref="excel-upload-input" class="excel-upload-input" type="file" accept=".xlsx, .xls" @change="handleClick">
    <div v-if="!btnModel">
        <div class="drop" @drop="handleDrop" @dragover="handleDragover" @dragenter="handleDragover">
            拖拽excel文件或
            <el-button :loading="loading" style="margin-left:16px;" size="mini" type="primary" @click="handleUpload">导入</el-button>
        </div>
    </div>
    <div v-else>
        <el-button :loading="loading" type="primary" @click="handleUpload">{{ btnText }}</el-button>
    </div>
  </div>
</template>

<script>
import XLSX from 'xlsx'

export default {
    name: 'uploadExcel',
    props: {
        btnText: {
            type: String,
            default: ''
        },
        uploadIndex: Number,
        btnModel: {
            type: Boolean,
            default: false
        },
        beforeUpload: Function,
        onSuccess: Function
    },
    data () {
        return {
            fileData: null,
            loading: false,
            excelData: {
                header: null,
                results: null
            }
        }
    },
    methods: {
        generateData ({ header, results }) {
            this.excelData.header = header
            this.excelData.results = results
            this.excelData.index = this.uploadIndex || 0
            this.excelData.fileData = this.fileData || null
            this.onSuccess && this.onSuccess(this.excelData)
        },
        handleDrop (e) { // 拖拽
            e.stopPropagation()
            e.preventDefault()
            if (this.loading) return
            const files = e.dataTransfer.files
            if (files.length !== 1) {
                this.$message.error('Only support uploading one file!')
                return
            }
            this.fileData = files[0]

            if (!this.isExcel(this.fileData)) {
                this.$message.error('Only supports upload .xlsx, .xls, .csv suffix files')
                return false
            }
            this.upload(this.fileData)
            e.stopPropagation()
            e.preventDefault()
        },
        handleDragover (e) {
            e.stopPropagation()
            e.preventDefault()
            e.dataTransfer.dropEffect = 'copy'
        },
        handleUpload () {
            this.$refs['excel-upload-input'].click()
        },
        handleClick (e) {
            const files = e.target.files
            this.fileData = files[0]
            if (!this.fileData) return
            this.upload(this.fileData)
        },
        upload (rawFile) {
            this.$refs['excel-upload-input'].value = null

            if (!this.beforeUpload) {
                this.readerData(rawFile)
                return
            }
            const before = this.beforeUpload(rawFile)
            if (before) {
                this.readerData(rawFile)
            }
        },
        readerData (rawFile) {
            this.loading = true
            return new Promise((resolve, reject) => {
                const reader = new FileReader()
                reader.onload = e => {
                    const data = e.target.result
                    const workbook = XLSX.read(data, { type: 'array' })
                    const firstSheetName = workbook.SheetNames[0]
                    const worksheet = workbook.Sheets[firstSheetName]
                    const header = this.getHeaderRow(worksheet)
                    const results = XLSX.utils.sheet_to_json(worksheet)
                    this.generateData({ header, results })
                    this.loading = false
                    resolve()
                }
                reader.readAsArrayBuffer(rawFile)
            })
        },
        getHeaderRow (sheet) {
            const headers = []
            const range = XLSX.utils.decode_range(sheet['!ref'])
            let C
            const R = range.s.r
            for (C = range.s.c; C <= range.e.c; ++C) {
                const cell = sheet[XLSX.utils.encode_cell({ c: C, r: R })]
                let hdr = 'UNKNOWN ' + C
                if (cell && cell.t) hdr = XLSX.utils.format_cell(cell)
                headers.push(hdr)
            }
            return headers
        },
        isExcel (file) {
            return /\.(xlsx|xls|csv)$/.test(file.name)
        }
    }
}
</script>

<style scoped>
    .upload-excel {
        display: inline-block;
    }
    .excel-upload-input {
        display: none;
        z-index: -9999;
    }
    .drop {
        border: 2px dashed #bbb;
        width: 600px;
        height: 160px;
        line-height: 160px;
        margin: 0 auto;
        font-size: 24px;
        border-radius: 5px;
        text-align: center;
        color: #bbb;
        position: relative;
    }
</style>
